The Toyota RAV4 EV uses a NiMH battery pack. Some of these vehicles are more than ten years old and have accumulated more than 100,000 miles without needing new batteries. So why are car companies telling us that battery technology is 'not there yet?'

NiMH Batteries: Obsolete Technology or Suppressed EV Solution?

Nobody supports electric vehicle development more enthusiastically than Sherry Boschert. During a recent interview, she told me, “We’ve got about a ten-year
window to stop burning carbon. After that, the worst effects of global warming due to greenhouse gas emissions will be unavoidable. We need to get lots of
plug-in hybrids (PHEVs) on the road, and we need to do it RIGHT NOW!”

Boschert’s book, Plug-In Hybrids, The Cars That Will Recharge America is an eloquent, meticulously-researched work that lays out not only the history of PHEVs, but also a roadmap to making them a ubiquitous mode of transportation for Americans in the very near future. In the book, Boschert describes many obstacles hindering widespread production of PHEVs, but none are more important to her than the difficulties that EV developers encounter when they try to obtain large-format nickel metal hydride (NiMH) batteries. She details the series of events which ultimately resulted in Chevron Oil gaining control of the patents covering most large-format NiMH batteries. While she does not accuse Chevron explicitly, the implication is clear; Chevron, and the combined strength of the oil/automotive industrial complex, now controls the production of these batteries and they are going to squash the technology flatter than Los Angeles’s “Red Cars,” the streetcars which used to transport Angelinos everywhere until automotive interests allegedly bought them and dismantled the system.

Others agree wholeheartedly with Boschert’s conclusions. EV activist Doug Korthof recently referred to EVs using NiMH batteries as “the ONLY solution to global warming”. This controversy burns up an amazing amount of bandwidth on the blogosphere. Type “PHEV NiMH patent suppression” into your internet search engine and prepare for an avalanche of hits, ranging from well-researched arguments from the Green Car Congress to rantings from conspiracy theorists who seem to place more emphasis on emotion than facts. The activist crowd is firmly convinced that NiMH batteries could help save the planet if they were only given the chance.

But what about the people who build batteries and electric vehicles? Nobody at Cobasys, the company who officially owns the large-format NiMH battery patents, responded to my request for an interview. However, I did speak with several people who have a great deal of experience designing and building electric vehicles. Professor Andy Frank at University of California, Davis, has spent decades building a series of electric vehicles with teams of students. He has led groups building both vehicles which run solely on batteries (BEVs) and PHEVs. His teams have used both NiMH batteries and lithium ion (Li-Ion) batteries in their projects.

I asked Frank if Li-Ion batteries, which can store twice as much energy as NiMH batteries of the same weight, have rendered NiMH batteries technologically obsolete. “Not yet,” he responded. I asked him if the design of NiMH batteries is more mature than the design of Li-Ion batteries. “Yes, but Li-Ion is catching up fast.”

I went on to ask about the cost of Li-Ion batteries versus the cost of NiMH. Frank speculated about near-term cost trends, assuming both were mass-produced in similar quantities. “The present thinking is that they will be comparable in cost per kW*h but they [Li-Ion] are one half the weight.”

However, Frank has not dismissed NiMH batteries entirely. He acknowledges that they make more sense in PHEVs than BEVs because PHEVs do not rely solely on their battery packs to determine the ultimate range. He also praised the durability of NiMH batteries. “The metal hydride batteries I have are over ten years old and they still work. Lithium chemistry is too new to tell.”

Other “technical types” tend to be even more pro-lithium than Frank. JB Straubel, chief technical officer at Tesla Motors, feels that NiMH batteries are nearly obsolete “given the increasing performance and falling price of Li-Ion.”

Tom Gage, president of EV-maker AC Propulsion, echoes Straubel’s thoughts. When I asked him if NiMH batteries were obsolete, he said “For hybrids, no. For full-function EVs, probably yes.”

Frank, Gage and Straubel all agree that the safety issues associated with lithium batteries have been solved through refinement in battery chemistry and implementation of computer-controlled battery management systems. Straubel points to a white paper on the subject, available on the Tesla website. Gage believes that Li-Ion batteries are safe, but that overly-enthusiastic media attention might create a false impression of danger. “The perceived safety will depend on the how serious the inevitable events are and how they are portrayed in the press.”

Gage also believes that the performance and safety of Li-Ion batteries will continue to evolve in the future. “I believe there will be a beneficial convergence of the high-safety [lithium] batteries like Valence and the high-energy batteries like commodity 18650s as Li-Ion cells are optimized for vehicle applications.”

It is also important to note that there are large-format NiMH batteries available which are not subject to control by the Cobasys patents. Electro Energy Inc. and Nilar Inc. both manufacture large-format NiMH batteries, but the bipolar design used in these batteries is fundamentally different from the design of the Cobasys batteries, so these batteries can be produced without paying licensing fees to Cobasys. Both companies are actively building batteries. Electro Energy works primarily on contract-based projects, but Nilar is selling batteries to multiple customers and is actively recruiting EV designers and builders to use their product.

I asked Richard Howlett, director of programs at Nilar, whether the company is concerned with regards to patent infringement issues. His answer was carefully crafted and approved by the company lawyers. “Our patent counsel and others have carefully reviewed the patent landscape relevant to our products and we, to our knowledge based on publicly available material, do not infringe on the intellectual property of any other company.”

It would seem that most technical people tend to look beyond the patent controversy surrounding NiMH batteries. Whether they look to Li-Ion, bipolar NiMH or any other battery design, their emphasis is on working with the batteries that best suit the requirements for an electric vehicle. While most “techies” admit that standard NiMH batteries covered by the Cobasys patents work acceptably well in PHEVs, their creative energy tends to be focused on Li-Ion batteries and other chemistries which can store more energy in much smaller packages.

As a proud techie, I am inclined to agree with the likes of Gage and Straubel. I have spent years working with various different battery types, and I have actively taken part in the design and manufacture of widely-used battery management systems. I know that lithium-ion batteries can be made to operate safely in electric vehicles. Furthermore, I know that Li-Ion cells are immediately available from a variety of sources. Additionally, any number of engineers could design inexpensive packaging for the Li-Ion cells that would allow them to be sold and installed as modules made up of multiple cells. Instead of using hundreds or thousands of individual cells in an EV, companies could purchase a drastically-reduced number of modules, each of which could come with its own battery management interface. These modules would communicate to a central controller, ensuring safe, optimized operation. Finally, I am certain that Li-Ion cells are available right now and that the price of Li-Ion batteries is falling quickly. Increased production will continue the trend toward lower price, and this trend will be very rapid if demand increases dramatically.

Still, I appreciate Sherry Boschert and the other NiMH proponents of the world. Perhaps their campaign played a role in General Motors’ recent decision to use Cobasys NiMH batteries in a soon-to-be-released Saturn hybrid SUV. These people are working hard to achieve the same goal as the techies. We are all trying to make sure electric vehicles, whether they be BEVs or PHEVs, become the “standard” automobile in the very near future. We are pursuing parallel paths to the same destination and harnessing the energy and intelligence of many good minds on either path.

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